Add EventHandlerRegistry

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index c09c01c5755f87eab0487d5af1a31e37ae6fe59b..bfb9b25d2e7c2bef6a47e49b89a107253cac8d16 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -30,6 +30,7 @@
 #include "RuntimeEnabledFeatures.h"
 #include "core/dom/Document.h"
 #include "core/dom/Node.h"
+#include "core/dom/ScrollEventHandlerController.h"
 #include "core/dom/WheelController.h"
 #include "core/html/HTMLElement.h"
 #include "core/frame/FrameView.h"
@@ -623,11 +624,22 @@ void ScrollingCoordinator::setWheelEventHandlerCount(unsigned count)
         scrollLayer->setHaveWheelEventHandlers(count > 0);
 }
 
+void ScrollingCoordinator::setScrollEventHandlerCount(unsigned count)
+{
+    if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling()))
+        scrollLayer->setHaveScrollEventHandlers(count > 0);
+}
+
 void ScrollingCoordinator::recomputeWheelEventHandlerCountForFrameView(FrameView*)
 {
     setWheelEventHandlerCount(computeCurrentWheelEventHandlerCount());
 }
 
+void ScrollingCoordinator::recomputeScrollEventHandlerCountForFrameView(FrameView*)
+{
+    setScrollEventHandlerCount(computeCurrentScrollEventHandlerCount());
+}
+
 void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons reasons)
 {
     if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling())) {
@@ -797,6 +809,18 @@ unsigned ScrollingCoordinator::computeCurrentWheelEventHandlerCount()
     return wheelEventHandlerCount;
 }
 
+unsigned ScrollingCoordinator::computeCurrentScrollEventHandlerCount()
+{
+    unsigned scrollEventHandlerCount = 0;
+
+    for (LocalFrame* frame = m_page->mainFrame(); frame; frame = frame->tree().traverseNext()) {
+        if (frame->document())
+            scrollEventHandlerCount += ScrollEventHandlerController::from(*frame->document())->scrollEventHandlerCount();
+    }
+
+    return scrollEventHandlerCount;
+}
+
 void ScrollingCoordinator::frameViewWheelEventHandlerCountChanged(FrameView* frameView)
 {
     ASSERT(isMainThread());
@@ -805,6 +829,14 @@ void ScrollingCoordinator::frameViewWheelEventHandlerCountChanged(FrameView* fra
     recomputeWheelEventHandlerCountForFrameView(frameView);
 }
 
+void ScrollingCoordinator::frameViewScrollEventHandlerCountChanged(FrameView* frameView)
+{
+    ASSERT(isMainThread());
+    ASSERT(m_page);
+
+    recomputeScrollEventHandlerCountForFrameView(frameView);
+}
+
 void ScrollingCoordinator::frameViewHasSlowRepaintObjectsDidChange(FrameView* frameView)
 {
     ASSERT(isMainThread());
@@ -855,6 +887,7 @@ void ScrollingCoordinator::frameViewRootLayerDidChange(FrameView* frameView)
 
     notifyLayoutUpdated();
     recomputeWheelEventHandlerCountForFrameView(frameView);
+    recomputeScrollEventHandlerCountForFrameView(frameView);
 }
 
 #if OS(MACOSX)